WTF Python: Exploring and understanding Python through surprising snippets

Post by CivBase » Thu, Feb 11, 2021, 4:45 PM UTC

bdg wrote: post #137

CivBase wrote: post #124

Earlier quoted context omitted.

What does a line length of 80 have to do with punch cards? My understanding is that 80 was originally chosen because that was the standard number of columns on a terminal. It has been continued to be used because it happens to be roughly just under half the width of a typical 16:9 or 16:10 monitor at normal font sizes, making it ideal for window snapping and side-by-side diffs. I have to review code in other language…

It's actually 79 chars. > the standard number of columns on a terminal are inherited from punched cards. https://stackoverflow.com/a/4651037/257493 But in 2021 I can resize my TTY Emulator, we have better fonts, and screen proportions have changed. A column length of 80 is in the ancestral DNA of computers because it was the number that packed nicely onto a sheet of paper. That paper was that size because it fit nice…

Post by TomSwirly » Thu, Feb 11, 2021, 6:02 PM UTC

Doxin wrote: post #12

I feel like WTFs caused by doing something deeply weird hardly counts against the language. Yes doing the walrus operator inside brackets works. Yes of course it's going to be doing weird things. Is this really surprising to anyone? It's not what that operator is for . Yes comparing strings with "is" works sometimes . It's not checking equality and it isn't supposed to. In another implementation using "is" might work…

Post by tgbugs » Thu, Feb 11, 2021, 6:32 PM UTC

silvester23 wrote: post #93

tgbugs wrote: post #47

Earlier quoted context omitted.

There are some that you can find in [0], but they are often de-contextualized (and sometimes aren't really Python's problem, because there was a trade off that had to be made, and the LOL is just frustration as a result of the bad ergonomics that it creates), those and some others will eventually go in an longer post when I finally get that set up. To give one concrete example of an LOL PYTHON consider the @property…

If I understand correctly, I think the problem with your second example is that you should avoid checking for `True` with something like `if isFile` but instead `if isFile is True`. That would solve this specific problem (and is also slightly more efficient because no implicit boolean conversion is performed).

    class Here:
        @property
        def booleanPredicate(self):
            return random_bool()


    class There:
        def anotherBooleanPredicate(self):
            return random_bool()
    
    here = Here()
    there = There()

    here.booleanPredicate           # as expected
    here.booleanPredicate()         # loud failure
    here.anotherBooleanPredicate    # silently always True
    here.anotherBooleanPredicate()  # as expected

Post by wynck » Thu, Feb 11, 2021, 7:38 PM UTC

Doxin wrote: post #12

I feel like WTFs caused by doing something deeply weird hardly counts against the language. Yes doing the walrus operator inside brackets works. Yes of course it's going to be doing weird things. Is this really surprising to anyone? It's not what that operator is for . Yes comparing strings with "is" works sometimes . It's not checking equality and it isn't supposed to. In another implementation using "is" might work…

Post by th0ma5 » Thu, Feb 11, 2021, 8:15 PM UTC

eyelidlessness wrote: post #7

th0ma5 wrote: post #3

Earlier quoted context omitted.

That one was all cynicism that baited the experienced and confused and discouraged beginners... this one actually takes the important next step of making it all teachable which is really great.

Oh come on Gary literally runs a top notch teaching site and the link was a bit of fun on his previous teaching site.